Tesla Motors has just picked up a $30 million investment from Japanese electronics giant Panasonic. The two companies announced late on Wednesday that Panasonic — a preferred battery cell supplier for Tesla’s electric vehicles — has bought a $30 million stake in the Palo Alto, Calif.-based car maker.

Panasonic made the investment through a private placement of common stock priced at $21.15 per share, according to a release from Tesla, and it now holds about 2 percent of the company.

It was back in January of this year that the Tesla and Panasonic first announced plans to work together developing nickel-based lithium-ion battery cells for electric vehicles, and for Panasonic’s cells to be used for Tesla’s “current and next-generation EV battery pack.” For months prior to that, Panasonic was rumored to be a battery cell supplier for Tesla’s planned Model S sedan.

This comes amid a much larger campaign by Panasonic to bolster its energy storage business and become a heavyweight player in the world of electric cars, shifting its focus away from the consumer electronics market. By early 2010, Panasonic had reached about halfway point in what it expects to be a $1 billion investment over three years in facilities for lithium-ion cell research, development and production.